This invention relates to a mechanical seal.
The mechanical seal, which accomplishes sealing by slidably contacting the end faces of a rotary ring and a non-rotary ring, is widely used as seal equipment in various fields.
The rotary ring rotates in association with rotation of a rotary shaft on which the ring is mounted, and the non-rotary ring does not rotate because it is fixed in the casing side. However, since the non-rotary ring is in contacting condition with the rotary ring and receives turning force by friction resistance, a stop for preventing the rotation of the non-rotary ring is necessary.
Further, it is required that at least one ring of said rotary and non-rotary rings must be slidable in the axial direction of the shaft and it must be pressed by a spring in the direction toward the slide end faces in order to cope with abrasion of the slide end faces and vibrations and to keep the contact pressure of the slide end faces. The mechanical seal where the non-rotary ring is slidable is called a static mechanical seal.
The conventional mechanical seal as shown in FIG. 3 adopts the composition where a compression ring 50 is set on the end of a non-rotary ring 61, a stop pin 51 is equipped on the compression ring 50 and the non-rotary ring 61 is pressed by spring 52 toward a rotary ring 60. However, in case of the conventional composition, the stop pin 51 makes the unit size long in the axial direction and it is impossible to install the unit in spaces having a limited dimension.
Further, it is difficult to assemble the unit, and a middle flange 54 is necessary in addition to a flange 53, which increases the cost.
The present invention solves the problems of the prior art described above.
The mechanical seal of this invention comprises a rotary ring mounted on a rotary shaft and rotates in association with the rotary shaft, a non-rotary ring mounted in a casing slidably contacting with the rotary ring to form sealing faces, a compression ring stopped at least in a rotating direction at an outer circumference thereof by the casing for fixing the non-rotary ring in the rotating direction and for contacting with said non-rotary ring so as to transfer pressure force toward said rotary ring, and a spring contacted with said compression ring for biasing said non-rotary ring toward said rotary ring via said compression ring.
The mechanical seal of this invention does not need a stop for preventing the rotation of the compression ring because the compression ring itself is caught by the casing at the outer circumference and the movement in the rotating direction is prevented. Consequently, the mechanical seal unit can be shortened in the axial direction and can be easily assembled.
In the preferred embodiment, the compression ring stops said non-rotary ring in the rotary direction. The compression ring has a projection projecting in a radial direction at the outer circumference thereof and there is a flange having a groove that accepts said projection to stop the rotation and to allow an axial movement of said compression ring. A spring contacts at one end with said compression ring and at other end with said flange for pressing said non-rotary ring to said rotary ring via said compression ring. Such compression ring functions to prevent the rotation of the non-rotary ring and receives the pressure of the spring.
The invention is more advantageous when it is reduced to practice as a cartridge type of mechanical seal. In the cartridge type of mechanical seal, a wide usefulness is very important. The mechanical seal of the invention can decrease the length in the axial direction and can be installed in limited spaces. In such type of mechanical seal it is preferred that said flange has an opening the diameter of which is bigger than said compression ring, and in the opening a retainer ring for holding said non-rotary ring is mounted. With such construction, the flange may be one piece instead of two pieces as in the prior art.
In the preferable embodiment, the opening is in succession with said groove and said compression ring is inserted through the opening to the groove so as to put the projection into the groove. A retainer ring for holding said non-rotary ring is installed in said opening after said compression ring is mounted.